Resilient coupling for servomechanism control



March 5,1957

P. F. ROSSMANN RESILIENT COUPLING FOR SERVOMECHANI SM CONTROL FiledSept. 14, 1954 *INVENTOR. P82 197 ZFossrrfdfi,

Ir omvz/s United States Patent O RESILIENT COUPLING FOR SERVOMECHANISMCONTROL Peter F. Rossmann, Grosse Pointe Farms, Mich., assignor to HuppCorporation, Cleveland, Ohio, corporation of Virginia ApplicationSeptember 14, 1954, Serial No. 455,977

4 Claims. (Cl. 64-27) This invention relates to resilientcouplings, andmore particularly to a spring arrangement for use in power steeringmechanism control units and controls for similar servomechanisms. Thisapplication is related to copending'applications Nos. 383,041 and433,647, filed Septem ber 29, 1953 and June 1, 1954 respectively byStanford R. Ovshinsky and assigned to the assignee of the presentapplication.

In any servomechanism of the closed loop type it is necessary to dampout undesirable oscillations that may feed back and cause the actions ofthe mechanism to be too severe. such as are disclosed in the above twoapplications, springs or other resilient elements are used to transmittorque between the manually operated member and the driven member suchas a steering shaft. It is desirable that undesirable oscillations inthis resilient coupling be damped to avoid sudden momentary changes inthe electrical control system which might cause erratic power assisttothe vehicle wheels. Ordinary springs, whether of a torsion, compressionor other type have natural periods of vibration which may causeoscillations if damp ing is not provided.

It is an object of the present invention to provide an" improvedresilient coupling for use in power steeringmechanisms and similarservomechanisms which will minimize undesirable oscillations and thusinsure 'the smooth control of the servomechanism throughout its entirerange of operation.

It is another object to provide an improved resilient In the case ofpower steering mechanisms.

2,783,627 Patented Mar. 5, 1957 12. It will be understood however thatthe novel coupling may also be applied between other parts and for otheruses than that shown, within the scope of the invention. Hub 11 isrotatably mounted on shaft 12 by rheostat 16 and its contact arm 17 maybe connected by electrical conduits (not shown) to the electromagneticclutches of a power steering mechanism such as those;

shown in the aforementioned applications. It is not necessary forpurposes of the invention that the rheostat and contact arm be of thetype shown; any similar control unit for use in the electrical circuitof a servomechanism may be present.

In the illustrated embodiment, rheostat 16 is secured to hub 11 by meansof a U-shaped bracket 18, one leg of which is secured to hub 11 byfasteners 19. The other leg of bracket 18 is secured by nuts 21 to athreaded coupling of this type which utilizes torsion or cantilever typesprings and which provides novel means for damping such springs toprevent undesirable oscillations.

It is also an object topr'ovide an improved resilient coupling havingthe above characteristics, in which the novel damping means is easilyinstalled, is of compact and dependable construction and is inexpensiveto fabricate.

Other objects,-feat ures, and advantages of the present invention willbecome apparent from the subsequent description, taken in conjunctionwith the accompanying drawings.

In the drawings:

Figure 1 is a cross-sectional view in elevation taken along the line 11of Figure 2 and showing a steering Wheel hub and steering shaft with theimproved resilient coupling of this invention, together with a controlrheostat for the power steering mechanism;

Figure 2 is a front elevational view of a portion of the mechanism ofFigure 1 taken in cross section along the line 2-2 of Figure 1 andshowing the configuration of one of the damping cams, the other cambeing omitted for purposes of clarity; and

Figure 3 is a fragmentary cross-sectional view taken along the line 3-3of Figure 1 and showing the lost motion safety connection between thesteering wheel and steering shaft.

The flexible coupling is shown as mounted between a hub -11'of a vehiclesteering wheel and a steering shaft tions.

nipple 22 which extends from rheostat 16. Steering shaft 12 has aconnecting member 23 secured to the rear end thereof by fasteners 24 ina'manner later described in detail. A contact arm shaft 25 is secured toconnecting member 23 by a set screw 26 which allows axial adjustmentthereof, and the outer end of shaft 25 has contact arm 17 secured,thereto. A bushing 27 is disposed between nipple 22 and shaft '25. Itwill therefore be seen that rheostat 16 will follow the movements ofsteering wheel hub 11, while contact arm 17 will move with steeringshaft 12. Any angular displacement between the hub and shaft, asdetermined by forces exerted on them and the resilient coupling, willresult in equivalent angular displacement between rheostat 16 andcontact arm 17.

The resilient coupling between the steering wheel and steering shaftcomprises a pair of torsion or cantilever springs 28 and 29 which are soarranged as to resist relativemovement of the wheel and shaft inopposite direcbracket 31 by fasteners 24. The bracket has a pair ofslots 33 and 34 within which one end of each spring issecured; Inparticular, end 35 of spring 28 is secured in slot-33- (spring 29 is notfully visible in Figure 2 because it is behind spring 28), and end 36 ofspring 29 is secured within slot 34. Ends 35 and 36 of the springs arebent inwardly for securing purposes, as seen in Figure 2. The springsextend in opposite directions from their securing points on bracket 31,spring 28 extending clockwise as seen in Figure 2- and spring 29extending counterclockwise.

Means are providedfor connecting the opposite ends of the springs to thesteering wheel so that relative angular' movement of the wheel and shaftin one direction will cause spring 28 to wind, and relative movement .in

the opposite direction will wind spring 29. This means comprises abracket 37 secured to hub 11 within recess 15 by fasteners 38. A pair ofposts 39 and 41 are secured to bracket 37 and extend outwardlytherefrom. The end of spring 28 adjacent post 39 has an outwardly Vhooked portion 42 which engages post 39. Likewise, the end of spring 29adjacent post 41 has a hook-shaped Each spring is of substantiallycircular flat shape 3 portion 43' en'gagin'g this"postf The connectionbetween posts*39*and" '41 'and' their adjacent'spring ends arwsuch thateach post can cause winding of its spring but cannot deflect the springin an unwinding direction Thus when; hub-"11 is turned' clockwise from iit's ieentral' ort 5 neutrah-position in-'Figure"2 'with bracket '31heldfsteht tio'nary;'post '39will ten'dto wind spring 28f deflectinggiittowardthe"dot=dash" position' shown. At the sametime post 41 will movetoward itsdot dashpositionaway'front" hookedportion 43 of spring29.

Means are provided for restraining the spring, ends '42 and'543 againstunwinding movement mama-err respec tive"p,ost's" are moved" in anunwindingi direction. This 1 means comprises" apairofrestrainingmrernbers ;44"and" 455'? Oii'eendof restraining member441i's seeuredw'ithin" 5 slot 33 ofbracket '31, as seenin Figure" 2;audien e end of riremb'e'r :45?semest r-withi slbt 34. TheIresti'ai'ninginretnbers cross"each other," andltheir' outer endsfeni.gage ease 42*and 43"of fthe "springsj', infsu'ch" manner'a's I toprevent me s'prings 'from 'unwiridingbeyond their men tralpositibm asshown 'in Figure 2;" It shb'uldbeinotedf that restrainingmembers 44 and"45"1'in'.no wagimerrejre withithewvindingga'ction of their respectivespringstunder the-'infliieneeofposts 39 "and 41. Thus, whentti'etst'e'ring'wlieeliis turnediimthe clockwise direction with respectto"s't'eering shaft12,' it"acts' only-upon spring, 28l whenturnedibeyondits neutral position. Whentur'nedtcounter clockwisefromitsineutrahposition, onlyj spring; 2911s.. wound -whilespringZSremains stationary. Setf scre'ws'f arm -as use'di to: hold springends: 35and '36 and'Ire, 30 taiiiingfimentbers'miand fiinplace. a i

Ass'tated previously,means are providdfor damping the "oscillations of.springs 28 and: 29st) asto. prevent er-.- ratic movementofrheostat 16.and contact arml'TJ It'w willbe fappreciated that sincehub' 11 is'frecly,rotatable= onshaft 12' by: means of bearings 13 and14,the.natural:l peiiodtofvib'ration of springs 28"and"29 couldtcausetunwantedoscillations of the steering wheel with respecttoYthdsha'ft.-This could be initiatedlfor example,.if th e steering wheelis spun bythe operator or sud denlyvre- 40 leased so that no manual restraintisrprovide d, In such cases; springs' 'whic'h are left free to oscillatewith lthei r natnrahperiods 'of"'vibration couldcause the steering wheel.to'" rotate rapidly; back and forth with respect totheshaftQ Even ifsuch oseiilations are relatively-smallns in magnitudefwith respect tothe total movement-of -,.thesteeringwheelItlieir efiect-on the operationoftthe'serv mechanism; as determined bythe instantaneous electrical;values set p by rheostat 'lo 'and contact arm 17, could;well-produceunsatisfactory power assistance. I

Tlie"'nte'ans for preventing such .unwanted- -oscillations inithe"present embodiment of the. invention: comprise dampingjrireansfor'springs. 28 and ZQ which-prevent continued natural "vibrations of t thesprings by progressively" diminishing; the amplitude of such. vibrationsMom-particularly; this is accornplishediby progressively.

ch'ang'ingitlie effective length of each spring gas.- it is de.---flectedjre'sultin'g in a variable rate springlwhichahas a sel-dampingieffeeti. Two similarly shaped abutments :41: and;Sf'a'redistrosed adjacent springs; 28and29 respectively; 'A'st s'e'en';in Figure 2, which showsvonly abut mentfj i {forre'asons oflclarity,vthe abutmentseare oft cre'seent shapetiwith their open ends facingthetends ofi the 'spn'ngsf Abutment '48;- which cooperates with spring-29, l S positioned symmetricallyabout ayertical, axis withrespectto'abutment 4711 The abutments areseeuredtto 3 eaclrfoth erby'anyjsuitable means, or may he madeasanrntgralfmember; andare securedto steering. shat-n12 by radiais'pokes 49"bn'a hub 51'keyed to shaft 12.Tak ing abiitnrent 4Tas *anillustration, the outer -.sur'ia'ce 52 oftlii's ahutment is'so shaped .as" to present 'a progressively ncreasingfsp'ace"53 between this surface and spring I 28. -g'on1g' in'-'aclockwise direction in Figure 2} when the". spn'ng a's its-neutralposition: More articularly,fthe

portion of surface 52-'-=adjacent end '35 of spring 1875- syrsaear 4iengages the spring when the latter is in its'neutral position: Thespace*betweemabutmentWTand*spi-ing18' is progressively larger in aclockwise direction, and is largest at end 55 of the abutment adjacenthooked end 42 of the spring. Abutment 48, although not visible in Figure2, is similarly shaped .with. respect to spring 29. The end of abutment48 adjacent end 36 of spring 29 is inflen'gagem'enti with'- the spring 2when the latter: is'zl iiu its neutral position. Thea-space-betweenabutment 48 and spring 29is. progressively,largerain. a counterclock:wise direction as seenin Figure.2;"thespace.beinglargest adjacent hookedend 43 of spring 29( With this arrangement, it will be seen that windingof either spring from its neutral :positi'orr will cause'a progressivelygreater por-tioncof :the springto engage its adjacent abutment. Theefiective length of the spring thus becomes progressively shorter as itis wound, and the natural period of lvibration rof the.- spring,.will.,.vary;aecordingly. When the springisbeing.nnwoundflhe-reyersewillhappen that is, its effective length 'will b ecomeproagressively.longer. The relative diinensionsoflthe pgrts maybe such. that most orall of -fan abutment isengaged. by its adjacent spring when. it' reaches-its@limiting posit tion as described further below.. Thelprogressivechange in the natural period of vibration of the springrasaitrisdeflected .will have .a damping. effectl so that-thespring vibrations Iwill progressively diminish in amplitudeiit the springs are allowed tovibrate freely; 4

It" should be noted at this point that.thedamping'efiectof .abutments-47 and 48 does notinterfere-with the=function of springs 28 and 29 aspart oflthe servomechanismr As described more fullyin the-aforesaidcopending apy plications; the-resilient couplingtibetween steering wheelll andsteering shaft 12 serves to: make the relative angu-T lardis'placement of these two members-proportionalvtot the-relative torquesexerted on thern. This ratio, of; dis placement toitorque may be linearon non-linear,l theelecs: trical characteristics of control elements 16and-17 being: chosen accordingly; In the present instancerthe fact that:springs 28 and 29 vary in rate as they are-.woundlmeans: thatanon-linearratio will exist between torque andr'disa placement but thiswill not atfect the-usefulness of the flexible coupling as part. of theservor'nechanisma Safetysmeansare provided for insuringm direct driving:connection-betweenthub 11 and steering :shaft 12; means is similar tothat described in theaforesaidapplicastions' ancl provides-form'anualapplicationzof-efiort. in excess of the amount-available'from thepower' assist 'unit; In)the presentembodiment, this safety 10st motiouncon nection isshownain Figures 1 and 3 and: comprisestalngl 56=extending;outwardlylfrom .shaft '12;into a sector shaped recess 57in:hub11. Recess;57 is wider thanilugjfi andc permits angulardis'placemcnt-ofvthe hub with respect to the. shaft; until atheabutment engages ithe" sides of-xthef recess-x. ltcshould" he noted that even uponinitial'com ressicn otspringszs:29 manuarsteerin elrort is exerteddirectly fonth steering shaft throughthese springs' and that the lost motionconnection becomes operative only" when maximum spring deflection isattained? In operation; assuming that hub 11and'shaft 12are' intlieir-"neutr'alposition as shown in Figure 2; manuali turning of hub11' in' a clockwise"directio against resist ance"offe"redby shaft12'will result in deflection ofspring. 28. This deflection will beproduced by] the engagement of post39g secured to hubtll, withiend 42 0fspring 28, the opposite end 35 of this spring beingsecured. to shaft 12throughlb'racket'31. As the spring iswound itsefiective length'will beshortened by progressive "contact with abutment 47. Contact arm '17willmove'relativeto-rheostatl16 .an amountequal to the relative angulardisplaccmenttoft shaftlland hub 11, thus controllingrt-hepower assistmechanism to provide power assistance proportionall to the displacement.This power-assistance willtend -:10 bring'bflie partsback to theirneutralposition, as explained grease? more particularly in theaforementioned applications. As

spring 28 is brought back to its neutral position its effective lengthwill become progressively greater as it becomes disengaged from abutment47. During the winding and unwinding movement of spring 28, spring 29will be prevented from unwinding by restraining member 45, so that post41 will simply move away from end 43 of spring 29.

During this movement of the parts, should spring 28 at any time bepermitted free vibratory movement, for example by sudden release of thesteering wheel by the operator, this vibration will be damped by theaction of abutment 47 which continuously changes the rate of spring 28as it vibrates. The vibrations will thus be progressively diminished inamplitude and undesired oscillations of control elements 16 and 17 willbe prevented. A similar situation will obtain with respect to spring 29and its abutment 48. The resulting power assistance to the steeringlinkage will be free from erratic fluctuations while still beingresponsive to the operators needs.

While it will be apparent that the preferred embodiment of the inventionherein disclosed is well calculated to fulfill the objects above stated,it will be appreciated that the invention is susceptible tomodification, variation and change without departing from the properscope or fair meaning of the subjoined claims.

What is claimed is:

1. In a device of the class described, a driving memher, a drivenmember, a pair of leaf type springs connecting said members, one of saidsprings being adapted to transmit force when the driving member is movedfrom a neutral position in one direction, the other spring being adaptedto transmit force when the driving member is moved from said neutralposition in the opposite direction, an abutment adjacent each of saidsprings, each abutment having a surface closely adjacent one end of itscorresponding spring and progressively farther away from the remainderof said spring when said members are in their neutral position, relativemovement of said members from their neutral position causing theforcetransmitting spring to engage progressively larger areas of itscorresponding abutment surface whereby the rate of said spring isprogressively varied.

2. In combination, a rotary driving member, a rotary driven membercoaxial therewith, a pair of springs connecting said driving and drivenmembers, said springs being of a curved leaf type, one end of eachspring being connected solely to said driving member, the other end ofeach spring being connected solely to said driven member, saidconnections being such as to cause said springs alternately to transmitforces from said driving member to said driven member in oppositedirections, and a pair of curved abutments adjacent said springs, eachabutment being closely adjacent one end of its corresponding spring anda progressively greater distance from the remainder of said spring,whereby deflection of either spring causes the effective length of suchspring to be progressively varied.

3. In combination, a rotary driving member, a rotary driven membercoaxial therewith, a pair of curved leaf type springs connecting saidmembers, one end of each spring being secured solely to one of saidmembers, said springs extending in opposite directions from saidconnections, the opposite ends of said springs having oneway connectionssolely to the other of said members whereby said springs may bealternately wound during relative movement of said driving and drivenmembers in opposite directions, restraining means for preventingunwinding movement of said springs from said neutral position, anddamping means for said springs comprising a pair of curved abutmentsadjacent said springs, each abutment being closely adjacent one end ofits corresponding spring and progressively further away from theremainder of said spring, whereby deflection of each spring causes avariation in the efiective length of said spring.

4. In combination, a rotary driving member, a rotary drivenmember-coaxial therewith, said driving member being supported forrotational movement on said driven member, a pair of loop-shapedcantilever springs connecting said members, one end of each spring beingsecured solely to said driven member, the other end of each springhaving a one-way connection solely with said driving member whereby saidsprings may be alternately wound when the driving member is moved inopposite directions from a neutral position with respect to the drivenmember, restraining means for preventing unwinding movement of saidsprings from said neutral position, and damping means for said springscomprising a pair of curved abutments mounted on said driven member andsurrounded by said springs, each abutment being closely adjacent thatend of its corresponding spring which is secured to said driven member,the abutment being spaced progressively further away from the remainderof said spring whereby the efiective length of said spring is variedduring its deflection.

References Cited in the file of this patent UNITED STATES PATENTS

